Every night for the next week, set aside ten minutes before you go to sleep. Write down three things that went well today and why they went well. You may use a journal or your computer to write about the events, but it is important that you have a physical record of what you wrote. The three things need not be earthshaking in importance (“My husband picked up my favorite ice cream for dessert on the way home from work today”), but they can be important (“My sister just gave birth to a healthy baby boy”).

Next to each positive event, answer the question “Why did this happen?”

The proportion of patients who didn’t receive the recommended care dropped from seventy per cent to four per cent; the occurrence of pneumonias fell by a quarter; and twenty-one fewer patients died than in the previous year. The researchers found that simply having the doctors and nurses in the I.C.U. make their own checklists for what they thought should be done each day improved the consistency of care to the point that, within a few weeks, the average length of patient stay in intensive care dropped by half.